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18hp B&S choke question


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04-18-16, 09:59 AM   #1  
18hp B&S choke question

OK, as some here know, I have a new mower.
That mower has a standard choke lever, turtle to rabbit. Accordingly, RPMs go from idle to very fast if you move it.
That made me wonder.
In 2005 I bought 18hp Sears B&S engine riding mower.
Technically has same choke, lever and pics.
But I was NEVER able to move lever past mid line. If moved into higher RPMs area, engine simply dies. Moved below mid line - dies again.
As I said - it was like this out of the box.
Is it supposed to be that way? Been running like this for years and I simply presumed it's the way it's supposed to be.

 
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04-18-16, 11:28 AM   #2  
That doesn't sound like a choke. It sounds like a throttle control. The dying above and below the midline you're describing doesn't sound right, though. That is something you would usually attribute to fuel - something in the carburetor, air filter, maybe exhaust.

 
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04-18-16, 01:47 PM   #3  
OK, then it's throttle control. But I can go idle to full blast on the new mower, on generator - that Craftsman ALWAYS was like that. In the middle it has little notch, so that lever catches on it, and glyph of mowed grass. Go a millimeter up towards rabbit - engine starts dying right away. It's clearly choking.
As of the the last year or so carb leaks a little after shut down, so I installed fuel shut off valve. But that's it. Had that mower for will be 11 yrs in June.

 
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04-18-16, 01:53 PM   #4  
No, it's choke.
This is what mine has, very similar:

http://www.briggsandstratton.com/lam...ke_linkage.jpg

 
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04-18-16, 03:26 PM   #5  
Controlling the speed of an engine isn't a choke function where as the throttle is. In a generator you would have the no load (idle), then the higher speed (load) There isn't anything intermediate that I know of.

The photo you have, I believe is a two function lever. The first setting is choke for starting the engine, the second position is for the higher speed (higher rpms - throttle) and the turtle is the lower speed (throttle). When you come out of the choke position, the choke goes off. That setup is on a lot of the older B&S engines as well. The full throttle position is adjacent to the choke setting to aid in a clear out of the richer start setting, I would think. On those same engines, going past the slower throttle setting goes from low rpms to an ignition kill.

On your mower the kill would probably come from an ignition kill switch rather than a throttle position lever.

 
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04-18-16, 03:34 PM   #6  
On the problem you've described with the choking of the engine when you go past a point on the throttle lever, it's an indication the linkage on the throttle is messed up and bringing on the choke when the throttle is in the fast idle position.

Probably an adjustment would take care of it.

 
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04-19-16, 02:24 PM   #7  
I'll do it, Marj.
I went on B&S site yesterday and they had similar condition described. Fixes were to adjust the carb screw that controls the high RPM and choke/throttle linkage. Move lever to choke position, loosen the bracket holding linkage in place, move lever to high position, move choke or throttle to full open by hand, re tighten the linkage bracket screw.
What trips me off it was like this brand new. First thing I did was to try to "kick in the high gear". So it died. I just lived with it.

 
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04-19-16, 03:05 PM   #8  
That happens a lot more often than you'd think. Stuff just isn't always quite right out of the box. That picture you posted is probably showing part of the fix for that problem.

Get that sucker in sync and you'll have a snarling beast of a lawn mower.

 
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04-20-16, 04:32 PM   #9  
OK, now look at this:

https://www.youtube.com/watch?v=1WWpeyDbHjA

specifically, 1:50. If your engine has automatic choke, it automatically chokes your engine at full throttle.
Isn't that exactly what mine does? As in - supposed to?

 
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04-20-16, 04:36 PM   #10  
That is not exactly an "Auto" choke, it still has to be manually opened and closed for that matter. Today's "Auto" chokes require no operator interaction when working

But I agree on what might come out of the box. Most things are setup before being shipped to the dealer/seller. Only the final assembly is done at the end store and most all else is not double checked.


Just needs a bigger hammer
Peace

 
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04-21-16, 05:04 AM   #11  
That setup he's working on has two cables, one for the throttle and one for the choke. Yours does the same thing with one cable and two functions. As BFH pointed out the autochokes are different animals.

 
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04-21-16, 09:00 AM   #12  
OK, science aside, mine does have auto choke - well, the mechanical version of it. As in - a lever moves on the carburator when throttle handle is at full throttle. Also, where throttle handle is normally used, it says on the side "mow with handle in this position".
To be more descriptive, there is horizontal cable that is operated by throttle handle cable. That works fine full range. It's mounted on a metal plate and behind it is almost vertical long lever. When cable is pulled all the way to about 75% open throttle (I am mowing at 50% open) that lever starts moving and at full throttle cable pull is vertical and solid in place. I tried moving it.
I am pretty positive then it is made that way - to choke if throttle handle is placed in higher RPM. Why am not sure, but that's what is appears to be and explains, why it never went into high RPMs.

 
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04-21-16, 09:13 AM   #13  
Ok, it's not auto choke. It's governor. Prevents engine from going into high RPM.
Mine looks identical to what he has in this video:

https://www.youtube.com/watch?v=9rO8AvDrdeM

So I'll check on this weekend. Rains are coming, I better mow tonight as if my grass goes high/wet, I'll get stuck again

 
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04-21-16, 11:01 AM   #14  
You have the general idea. Yours is manual and when it is in the rabbit position, the choke plate and throttle plate should be open. When you move the lever on to the choke position, the choke plate should close and the throttle plate should stay open. Just adjust your linkage so that happens and you'll in great shape.

By being out of adjustment the functions are moved to the lower rpm side of the scale. All you have lost is the lower rpms settings for the lever. It becomes confusing since the functions don't line up with the indicators on the shroud.

The governor works between the throttle and the carburetor to control the rpms you select with the control lever. When you move a throttle control you're telling the governor to let more/less rpms through from the engine.

 
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04-23-16, 07:14 AM   #15  
Now that I knew what to Google for, final answer is - I'll let it be as is.
Word out, and loud and clear, is to NOT mess with governor. Reason being, found reports on folks doing this on purpose, to get more whoomp out of their mowers. Resulting in exploding flywheels and engines.
I'll pass.
Different thing is - why to make an engine and then set it on governor, knowing that it may break down, that beats me.

 
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